1. Field of the Invention
The invention relates to a welding process for connecting a preferably insulated winding wire of a coil to a terminal, including a metal sleeve being slipped over the terminal and the winding wire attached to the latter, and the metal sleeve, the terminal and the winding wire then being welded to one another under inert gas. The invention relates, furthermore, to a metal sleeve for use in this process.
2. Description of the Related Art
A preferred field of use of the present invention is coils for electromagnetic relays or similar switchgear. The windings of these coils consist, as a rule, of lacquer-insulated copper wires, a heat resistant lacquer insulation for the winding wires being necessary for use under relatively high thermal load. For contacting the winding ends with corresponding terminals, it has hitherto largely been customary to solder the stripped winding wire to the terminals. In addition to a complicated process technology in terms of the soldering baths and handling, the disadvantage of this soldering process is that the fluxes used for such process, in so far as they cannot be removed completely, can subsequently generate contact-impairing vapors in the switchgear.
Moreover, it is also already known to contact winding wires and terminals by means of a welded joint. In conventional welding processes, however, there is the risk that the copper alloys of the winding wires or of the terminals will become brittle and therefore be in danger of breaking. German Patent Application 39 11 027 has consequently already proposed a process of the type mentioned in the introduction, in which an arc-welding process is carried out under inert gas, a metal sleeve being welded over the terminal and the wound-on wire. This relates, however, to a sleeve which is open at both ends and which is slipped over the terminal as far as the anchor location of the terminal in the base body and is then also pressed onto the base body. There is a risk, here, that the wound-on winding wire will be pulled in an undesirable way and possibly be pinched between the metal sleeve and base body, thus resulting in the risk of subsequent breakage, for example in the event of temperature changes.